From: Mike Kravetz <firstname.lastname@example.org>
To: Oscar Salvador <email@example.com>,
Andrew Morton <firstname.lastname@example.org>
Cc: David Hildenbrand <email@example.com>,
Muchun Song <firstname.lastname@example.org>,
Michal Hocko <email@example.com>,
Subject: Re: [PATCH v3 1/2] mm: Make alloc_contig_range handle free hugetlb pages
Date: Thu, 25 Feb 2021 12:03:18 -0800 [thread overview]
Message-ID: <firstname.lastname@example.org> (raw)
On 2/22/21 5:51 AM, Oscar Salvador wrote:
> alloc_contig_range will fail if it ever sees a HugeTLB page within the
> range we are trying to allocate, even when that page is free and can be
> easily reallocated.
> This has proved to be problematic for some users of alloc_contic_range,
> e.g: CMA and virtio-mem, where those would fail the call even when those
> pages lay in ZONE_MOVABLE and are free.
> We can do better by trying to replace such page.
> Free hugepages are tricky to handle so as to no userspace application
> notices disruption, we need to replace the current free hugepage with
> a new one.
> In order to do that, a new function called alloc_and_dissolve_huge_page
> is introduced.
> This function will first try to get a new fresh hugepage, and if it
> succeeds, it will replace the old one in the free hugepage pool.
> All operations are being handled under hugetlb_lock, so no races are
> possible. The only exception is when page's refcount is 0, but it still
> has not been flagged as PageHugeFreed.
> In this case we retry as the window race is quite small and we have high
> chances to succeed next time.
> With regard to the allocation, we restrict it to the node the page belongs
> to with __GFP_THISNODE, meaning we do not fallback on other node's zones.
> Note that gigantic hugetlb pages are fenced off since there is a cyclic
> dependency between them and alloc_contig_range.
> Signed-off-by: Oscar Salvador <email@example.com>
I spent a bunch of time looking for possible race issues. Thankfully,
the recent code from Muchun dealing with free lists helps. In addition,
all the hugetlb acounting looks good.
Reviewed-by: Mike Kravetz <firstname.lastname@example.org>
> include/linux/hugetlb.h | 6 +++
> mm/compaction.c | 12 ++++++
> mm/hugetlb.c | 111 +++++++++++++++++++++++++++++++++++++++++++++++-
> 3 files changed, 127 insertions(+), 2 deletions(-)
next prev parent reply other threads:[~2021-02-25 20:03 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-22 13:51 [PATCH v3 0/2] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
2021-02-22 13:51 ` [PATCH v3 1/2] mm: Make alloc_contig_range handle free hugetlb pages Oscar Salvador
2021-02-25 20:03 ` Mike Kravetz [this message]
2021-02-26 9:48 ` Oscar Salvador
2021-02-26 8:35 ` Michal Hocko
2021-02-26 8:38 ` Michal Hocko
2021-02-26 9:25 ` David Hildenbrand
2021-02-26 9:47 ` Oscar Salvador
2021-02-26 9:45 ` Oscar Salvador
2021-02-26 9:51 ` Michal Hocko
2021-03-01 14:09 ` David Hildenbrand
2021-03-04 10:19 ` Oscar Salvador
2021-03-04 10:32 ` David Hildenbrand
2021-03-04 10:41 ` Oscar Salvador
2021-02-22 13:51 ` [PATCH v3 2/2] mm: Make alloc_contig_range handle in-use " Oscar Salvador
2021-02-25 23:05 ` Mike Kravetz
2021-02-26 8:46 ` Michal Hocko
2021-02-26 10:24 ` Oscar Salvador
2021-02-26 10:27 ` Oscar Salvador
2021-02-26 12:46 ` Michal Hocko
2021-02-28 13:43 ` Oscar Salvador
2021-03-05 17:30 ` David Hildenbrand
2021-03-01 12:43 ` [PATCH v3 0/2] Make alloc_contig_range handle Hugetlb pages David Hildenbrand
2021-03-01 12:57 ` Oscar Salvador
2021-03-01 12:59 ` David Hildenbrand
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